1. Field of the Invention
The present disclosure relates to a semiconductor device and, in particular, to a semiconductor device having transistors.
2. Description of the Related Art
For improving switching speed, conventional power supplies utilize field-effect transistors as switching devices. Further, field-effect transistors have lower resistance, and thus power efficiency is improved.
As shown in FIG. 1, conventional field-effect transistors A10 are arranged on a substrate A20. The field-effect transistors A10 are connected with each other in parallel to output greater current. Each of the field-effect transistors A10 includes a drain electrode A11, a source electrode A12, and a gate electrode A13. The drain electrode A11, the source electrode A12, and the gate electrode A13 are linear in structure and parallel to each other.
When the field-effect transistors A10 are installed in a high-voltage power supply with a voltage higher than 300V, the distance between the drain electrode A11 and the source electrode A12 is greater than 7 nm. However, in this structure, the sum of the gate width Wg of the gate electrode A13 on the substrate A20 is short, and the current outputting by the field-effect transistors A10 is smaller.
For increasing the gate width Wg, as shown in FIG. 2, the drain electrodes A21 and the source electrodes A22 of the field-effect transistors A20 are alternately arranged in an array. The drain electrodes A21 and the source electrodes A22 are squares, and the gate electrodes A23 are elongated rectangles around the source electrodes A22. However, since electrons flow along a shortest path in general, the electrons may not flow through the invalid areas Z1 in FIG. 2. Therefore, some areas in the substrate A20 are wasted. A greater area of the substrate A20 is needed to output the same current with the same numbers as the field-effect transistors A20, and as a result, manufacturing cost is increased.